The present disclosure relates generally to methods for producing cycloalkylidene bisphenols. More particularly, the disclosure relates to methods for producing cycloalkylidene bisphenols using macroreticular sulfonic acid type ion exchange resins as catalysts, and mercaptan and/or a resorcinol compounds as promoters.
Cycloalkylidene bisphenols are valuable raw materials for producing polycarbonates having enhanced properties, such as thermal stability, clarity, and dimensional stability in the presence of moisture. The para, para-isomers are particularly valuable in this regard. Cycloalkylidene bisphenols have generally been prepared by a condensation reaction of an aromatic hydroxy compound with a cycloalkanone using an acid catalyst to catalyze this reaction. In addition to the acid catalyst, a promoter is also used to further aid the reaction. Mineral acids, such as hydrochloric acid or sulfuric acid have been generally used for producing cycloalkylidene bisphenols as promoters.
Sulfonic acid type ion exchange resin catalysts, particularly the so-called gelular ion exchange resin catalysts, which are crosslinked with up to 4 weight percent of divinylbenzene have been widely used as catalysts for preparing aromatic dihydroxy compounds. For example, gelular ion exchange resins have been used in conjunction with mercaptan compounds to produce para, para-bisphenol A, which is one of the more important aromatic dihydroxy compounds used for producing polycarbonate homopolymers and copolymers. Although the gelular resins perform satisfactorily for bisphenol A, they exhibit low selectivity and reactivity for producing cycloalkylidene bisphenols, and in particular, the para, para-isomer. Prior art gelular resins crosslinked at less than or equal to about 4 weight percent of DVB are used in a continuous process for producing bisphenols, particularly bisphenol A, compression of the catalyst particles due to hydrostatic pressure occurs, and this hydraulically limits the process.
Accordingly, there remains a need in the art for more efficient methods to prepare cycloalkylidene bisphenols, which exhibit improved selectivity and reactivity than gelular resins.